Air cooling for radial engines



pt. 2, 194?. L. s. HOBS AIR coomm FOR RADIAL mamas Filed May 22,1942

INVENTOR ai d Sflwbbs ATTORNEY.

Patented Sept. 1947 2,426,871 AIR. COOLING FOR RADIAL ENGINES Leonard S. Hobbs, West Hartford, Conn., assignor to United ford, Conn., a

Aircraft Corporation, East Hartcorporation of Delaware Application May 22, 1942, Serial No. 444,062

8 Claims. I

This invention relates to improvements in internal combustion engines with particular reference to radial air-cooled aircraft engines.

An object of the invention resides in the provision, in an engine of the character indicated, and having a large number of cylinders arranged around a central crankcase, of improved means for distributing cooling air among the various engine cylinders, which ar understood to be provided with cooling fins.

A further object resides in the provision, in an engine of the character indicated, of a cylinder arrangement such that the grouping of the cylinders about the crankcase and the distribution of cooling air among the cylinders is greatly facilitated.

Other objects and advantages will be apparent from the specification and references, and from the accompanying drawing, which illustrates what is now considered to be a preferred embodiment of the invention.

In the drawing:

Fig. l is a diagrammatic elevation view of a portion of an engine of the character indicated showing the arrangement of the cylinders and the application thereto of cooling air guides or baflies for distributing the air among the various engine cylinders, and

Fig. 2 is a diagrammatic the engine cylinders and the rangement shown in Fig. 1.

Referring to the drawing in detail, the numeral generally indicates the engine crankcase which may be of a suitable form to carry the various cylinders as generally indicated at l2.

In the arrangement illustrated, there are four rows of cylinders as indicated at A, B, "C and D (Fig. 2) with seven cylinders in each row thus making a total of twenty-eight cylinders for the engine.

As is clearly illustrated in Fig. 2, the cylinders in each circumferential row are arranged in offset relation with respect to corresponding cylinders in adjacent rows thus providing cylinder banks extending generally fore-and-aft of the engine, which banks are not parallel to the engine axis but have a somewhat helical form, winding about the engine axis from. front to the rear of the engine. Between each two adjacent banks of engine cylinders there is a baifle plate or bulkhead, indicated at It, l6, l8 and 2|. Each of these plates is curved at its front end around a portion of the front cylinder of one bank and at its rear end around a portion of the rear cylinder of the adjacent bank. These baflies extend outwardly radially of the engine and each is provided along development view of cooling air bailie ar- I its outer edge with a circumferential extension l9 which overlies portions of the cylinder heads of the bank containing the cylinder which the rearward end of the baflle partially encloses. The cylinder heads are so constructed that portions of the flange part IQ of the bafile member may be which has an air entrance disposed at opposite sides of the central head portion 2| carrying the two rocker arm boxes 40, 42 and the port 38, which and may be closely fitted to this central part of the head so that the only exit opening for the cooling air is at the downstream side of the cylinder. These baflles thus provide along one side of each bank of cylinders a tapered air duct such as is clearly shown in Fig. 2 and indicated at 20. Between each two bank there is a baflle member of a substantially O-Gee shape, such as are indicated at 22, 24 and 26. These inter-cylinder bafiles, in combination with the corresponding inter-bank baflles, direct air around each cylinder of each bank. In th right-hand bank shown in Fig. 2 the air entrance openings for the various cylinders ar indicated at 28, 30, 32 and 34. Entrance 28 for the first cylinder opens to thefront of the engine enclosure while the openings 30, 32 and 34 for the next three cylinders open tothe tapered air duct 20 opening 36 also opening to the front of the engine between cylinders of the front row A. After the air has passed the cylinders through the inter-fin spaces, it fiows into the space between the cylinders and the elongated bailie on the downstream side of the cylinder bank, which is the bafile to the right of each cylinder bank in the arrangement shown in Fig. 2. From this space the air flows outwardly through the space between the adjacent elongated bafiles and past bafile extension i 9 into an annular space surrounding the engine within the engine cowl and thence to the outside atmospher In the arrangement illustrated, the cylinder exhaust stacks138 extend from the tops of the cylinder heads into the annular space surrounding the engine where they are cooled by the air after the air'has passed the engine cylinders.

The above described arrangement of cylinders and baiiies provides an efficient cooling air duct for each cylinder of the multi-cylinder engine and thus insures that each cylinder no matter whether it is positioned towards the front or towards the rear of requirement of cooling air. The ballles also force the air to flow in close contact with the cylinders and through the inter-fin spaces so thatno air is wasted and only the minimum volume of cooling air is required.

It will be noted from Fig. 2 that the staggered arrangement of cylinders permits fore-and-aft overlapping of rocker boxes 40 and 42 of adjacent cylinders of each bank thereby reducing the length of the engine to a minimum.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. In an air-cooled radial engine having a plumay be an exhaust D0rt,.

adjacent cylinders of each the engine will receive its full rality of cylinders extending radially from a central crankcase and arranged in at least three ,circumferentlal rows and in longitudinal banks with the cylinders in each bank progressively angularly displaced in the same direction, a ballle member extending from the front cylinder of each bank to the rear cylinder of the adjacent bank to provide along one side of each bank a rearwardly converging air flow passage, and an air guide baffle between each two adjacent cylinders in each banla;

2. A radial air-cooled engine having a fore-T and-aft crankshaft, fore-and-aft banks of spacedapart cylinders operatively connected to said shaft, each cylinder being circumferentially offset with reference to the cylinder ahead of it so that each bank of cylinders is arranged helically about said shaft, each bank having baiile plates on opposite sides thereof with a-flrst plate close to the cylinder at one end of the bank and spaced from the cylinder at the other end of the bank and a second plate close to the cylinder at said other end of the bank and spaced from the cylinder at said oneend of the bank, whereby the space for cooling air entering one side of the bank gradually decreases while the space for exhaust air on the other side gradually increases, and baflies between adjoining cylinders for guiding cooling air about predetermined portions of said cylinders.

3. A radial air-cooled internal combustion aircraft engine having a crankcase, a crankshaft in said crankcase, and finned cylinders carried by said crankcase, said cylinders being disposed radially around the axis of said crankshaft in four or more circumferential rows spaced along said crankshaft axis and in seven or more banks extending helically of said crankshaft axis, the cylinders in successive rows in each of said banks being displaced angularly around said crankshaft by increasing amounts relative to the first row cylinder of each said bank, the circumferential spacing between the first and last row cylinders in eachbank being less than the circumferential spacing between adjacent cylinders in said front row, radial bulkheads forming a cooling air passage for each bank having an inlet opening between adjacent first row cylinders on one side ofthe bank and an outlet opening on the other side of the bank, and baflles around each cylinder in the bank for guiding cooling air from said inlet across the bank to said outlet.

4. In an air-cooled radial engine having a plurality of circumferential rows of cylinders extending outwardly from a central crankcase, the rows being so arranged that corresponding fore and aft cylinders of the different rows constitute banks in which the cylinders are progressively anguiarly displaced to formspirals about the center line of said crankcase, each cylinder being provided with outwardly extending fore and aft valve rocker boxes, said boxes projecting into spaces between cylinders of adjacent rows, means including a baille between each two adjacent cylinders in each bank for guiding air around each side of each cylinder symmetrically with respect to said rocker boxes, and a bulkhead extending radially and longitudinally between each pair of adjacent cylinder banks.

5. In an air-cooled radial engine having a plurality of cylinders extending radially from a central crankcase and arranged in at least three 70 circumferential rows and in longitudinal banks with the cylinders in each bank progressively angularly displaced in the same direction, a bafiie member extending from the front cylinder of each bank to the rear cylinder of the adjacent 75 passages; and a separate air entrance opening at the front of said engine for each cylinder of the front row of engine cylinders.

6. In an air-cooled radial engine having a plurality of cylinders extending radially from a central crankcase and arranged in at least three circumferential rows and in longitudinal banks with the cylinders in each bank progressively angularly displaced in the same direction, a baiiie member extending from the front cylinder of each bank to the rear cylinder of the adjacent bank to provide along one side of each bank a rearwardly converging air flow passage, an air guide baiile between each two adjacent cylinders in each bank, and circumferential ballie plates extending from said baiile members and extending across the respective air flow passage to the cylinder heads of the adjacent bank of cylinders.

7. In an air-cooled radial engine having a plurality of cylinders extending radially from a central crankcase and arranged in at least three circumferential rows and in longitudinal banks with the cylinders in each bank progressively angularly displaced in the same direction, a baille member extending from ,the front cylinder of each bank to the rear cylinder of the adjacent bank to provide along one side of each bank a rearwardly converging air flow passage, an air guide baflle between each two adjacent cylinders in each bank, and circumferential baille plates extending from the outer edges of the longitudinal bafiles and across the inter-cylinder guide baffles.

8. In a radial aircraft engine having a crankshaft, a plurality of air-cooled cylinders arranged in at least four circumferential rows and at least seven spiral banks with respect to the axis of rotation of said crankshaft, a radial bulkhead between each pair of adjacent cylinder banks extending from the front cylinder of each bank to the rear cylinder of the adjacent bank in the general direction of said crankshaft axis and bridging the space between said pair of adjacent cylinder banks, each pair of adjacent bulkheads forming a cooling air passage which extends in the direction of said crankshaft axis and which is bridged by an interposed cylinder bank, and air guide baffles on opposite sides of each cylinder in each bank.

LEONARD S. HOBBS.

aaraanncas crran The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,070,565 Dintilhac Feb. 16, 1937 2,037,708 Davis Apr. 21, 1946 1,622,388 Masury et al Mar. 29, 1927 1,398,119 Edwards Feb. 21, 1933 1,982,126 Thaheld Nov. 27, 1934 2,270,912 Theodorsen Jan. 27, 1942 FOREIGN PATENTS Number Country 1 Date 175,554 England Feb. 23, 1922 486,371 England June 2, 1938 492,016 France June 26, 1919 306,942 Feb. 27, 1930 497,592 England Dec. 21, 1938 

